This invention relates to facsimile transmission systems and methods for sending a document between a sender and a receiver by facsimile in a manner which prevents unauthorized casual reading of the document, and, more particularly, to a device for photocopying a document employing a standard photocopy machine having a cover glass upon which documents to be copied are placed to produce two partial documents each containing portions of the document which are complementary and mutually exclusive, the device comprising a transparent sheet sized to be placed on the cover glass and having a pattern thereon of white and transparent portions which are complementary along longitudinally equal shift distances; holder means for holding a document over the pattern and disposed on the transparent sheet; and, moving means for moving the holder means between a first position and a second position located longitudinally at the equal shift distance from the first position.
In above-referenced, co-pending '700 application, the teachings of which are incorporated herein by reference, a method and associated apparatus is disclosed by means of which a document can be transmitted between a sender and a receiver by facsimile in a manner which prevents unauthorized casual reading of the document. The method and an associated mechanical apparatus for practicing the method are shown in simplified form in FIGS. 1-5. As depicted in FIGS. 1 and 2, a pair of patterns 10 and 12 are alternately placed over the document 14 while it is scanned (either by a photocopy machine or the scanning head of a facsimile machine). Each pattern 10, 12 contains white portions 16 on a transparent background thus creating transparent portions 18. The patterns 10, 12 are complementary and mutually exclusive; that is, the "A" pattern 10 of FIG. 1 has white portions 16 where the "B" pattern 12 of FIG. 2 has transparent portions 18, and vice versa. Thus, when the document 14 of FIG. 3 is scanned through the "A" pattern 10 of FIG. 1 the partial document 14' of FIG. 4 is produced. Similarly, when the document 14 of FIG. 3 is scanned through the "B" pattern 12 of FIG. 2 the partial document 14" of FIG. 5 is produced. The two partial documents 14', 14" are then transmitted by facsimile to the receiver. At the receiving end, the two partial documents 14', 14" are difficult to read and understand, at least to the casual observer. The intended receiver, however, makes a copy of one of the two partial documents 14', 14" and only has to place the transparent copy over the other partial document in proper registration in order to view (and copy, if desired) the reconstructed document 14.
The co-pending '700 application also discloses a method of creating the partial documents 14', 14" for facsimile transmission employing computer software. That, however, is not the area addressed by this invention. As can be appreciated, if two separate physical patterns 10, 12 are employed in scanning the document 14, registration of the document 14 on patterns 10, 12 can be a problem. Of course, if copying of the document 14 is not accomplished with the patterns 10, 12 in proper registration, the partial documents 14' and 14" will contain duplicate and missing information. The duplicate information is not a problem as it merely overlaps when the transparency overlay and registration process is accomplished by the receiver. Missing information, however, is missing forever. The problem of registration is particularly severe when non-rectangular documents of irregular size and/or shape are to be copied for secure transmission.
Wherefore, it is the object of this invention to provide a patterning device for use with the method of the co-pending '700 application which eliminates the registration problem and can be used with irregular sized and shaped documents.
Other objects and benefits of this invention will become apparent from the detailed description which follows hereinafter when taken in conjunction with the drawing figures which accompany it.